A Study on the Correlations between Dark Count and Photon Detection Efficiency According to P-Well Structure in GM-APD

[Introduction] The next-generation radiation device SiPM (Silicon Photomultiplier) is a combination of several hundred to several thousand micro cells comprised of GM-APD (Geiger Mode-Avalanche Photodiode) and quenching... [ view full abstract ]

[Introduction]
The next-generation radiation device SiPM (Silicon Photomultiplier) is a combination of several hundred to several thousand micro cells comprised of GM-APD (Geiger Mode-Avalanche Photodiode) and quenching resistor. The electric field generated at the pn junction directly influences photon detection efficiency (PDE) and dark count which are key performance indices of GM-APD. The criteria for optimized P-Well structure are presented in this paper.

[Methods]
When the maximum electric field of GM-APD increases, the PDE increases, but Band to Band Tunneling (BBT) and Trap Assisted Tunneling (TAT) among the causes of dark count increase in proportion to the intensity of the maximum electric field. The intensity of the maximum electric field varies according to the P-Well structure and a proper design of P-Well is critical in the determination of the performance of GM-APD. In this paper, the TCAD simulation of Silvaco was used to set energy and dose of the implantation, and simulation was conducted by varying the P-Well anneal time and temperature. The electric field distribution was extracted from the breakdown voltage based on the simulation results and the PDE and dark count were compared.

[Conclusion]
When the P-Well anneal time was shorter than 150 minutes, the maximum electric field was high, but the depth of P-Well was shallow, resulting in lower triggering probability and PDE. When the P-Well anneal time was longer than 150 minutes, the electric field decreased, resulting in lower PDE. The higher the P-Well anneal temperature was, the lower the maximum electric field became and the PDE tended to decrease. When the maximum electric field at the pn junction was lower than 5.6E5(V/cm), BBT became lower than TAT and the dark count rapidly decreased. In conclusion, the design of P-Well with 1000°C and 150 minutes will generate the maximum electric field of 5.6E5(V/cm) or lower, and high PDE and low dark count can be expected.

[Acknowledgments]
This study was funded by the Nano Open Innovation Lab partnership project of NNFC.